The package xxl.core.cursors.differences provides miscellaneous
implementations of the difference operator on cursors. This operation can
be performed in two different ways, on the one hand it removes an element
of the first input iteration if the same element exists in the
second one. On the other hand it removes all elements of the first input
iteration that match with an element of the second one. This second
approch implies that no duplicates will be returned by the difference
operator, whereas the first solution may contain duplicates if the number
of equal elements in the first input iteration is greater than that of
the second one.